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Search every question and quick fact in the course.

Everything, A to Z (280)

1-bit counts for every number from 0 to n Question · Bits and maths
[[0] * n for _ in range(m)] Quick fact · Dynamic programming
A stack that also reports its minimum Question · Stacks and queues
Add a booking to a sorted list of separate blocks Question · Greedy choices and intervals
Adjacency list size Quick fact · Graphs
Adjacency list, adjacency matrix or edge list? Question · Graphs
Amortised cost: cheap on average, sometimes slow Question · Complexity analysis
Answer many range-total questions quickly Question · Complexity analysis
Apply the backspaces in typed text Question · Stacks and queues
Are two trees identical? Question · Trees
Area of the biggest patch of land Question · Graphs
assert for quick tests Quick fact · Interview craft
Best haul when the lockers form a ring Question · Dynamic programming
Best haul without opening two neighbouring lockers Question · Dynamic programming
Best single buy-then-sell on a price history Question · Sliding window
Best total over k consecutive days Question · Sliding window
Best, average and worst case Question · Complexity analysis
BFS or DFS: which one to use Question · Graphs
Big O in plain words Question · Complexity analysis
Binary search on the answer Question · Searching sorted data
Binary search without off-by-one bugs Question · Searching sorted data
bisect key argument Quick fact · Searching sorted data
bisect.bisect_left Quick fact · Searching sorted data
bisect.bisect_right Quick fact · Searching sorted data
Bit tricks worth knowing Question · Bits and maths
Brute force first, then improve Question · Interview craft
Build a queue out of two stacks Question · Stacks and queues
Busiest hour in each k-hour span Question · Sliding window
Cache arguments must be hashable Quick fact · Dynamic programming
Can a string be split into dictionary words? Question · Dynamic programming
Can every task finish, given its prerequisites? Question · Graphs
Can you hop to the last tile? Question · Greedy choices and intervals
Cells whose rain reaches both coasts Question · Graphs
Cheapest route from top-left to bottom-right Question · Dynamic programming
Cheapest way to cable every office together Question · Graphs
Cheapest way to join ropes into one Question · Heaps and priority queues
Closest shared ancestor in a search tree Question · Trees
collections.deque Quick fact · Sliding window
collections.deque Quick fact · Stacks and queues
collections.deque Quick fact · Linked lists
collections.deque for BFS Quick fact · Trees
Combine overlapping bookings into blocks Question · Greedy choices and intervals
Copying the path Quick fact · Backtracking
Count or sort: choosing a frequency tool Question · Arrays, strings and hash maps
Count position pairs whose values differ by exactly k Question · Interview craft
Count sales stretches that add up to a target Question · Arrays, strings and hash maps
Count the 1 bits in a number Question · Bits and maths
Count the picks that hit an exact total Question · Backtracking
Count the separate patches of land on a map Question · Graphs
Count the stretches that read the same backwards Question · Strings and tries
Count the ways to place queens that cannot attack Question · Backtracking
Count weight triples that stay under a limit Question · Two pointers
Cut a string into the most chunks so no letter crosses a cut Question · Greedy choices and intervals
Cut a word into pieces that each read the same backwards Question · Backtracking
@dataclass Quick fact · Trees
@dataclass(eq=False) Quick fact · Linked lists
deque(maxlen=k) Quick fact · Sliding window
Dict order Quick fact · Arrays, strings and hash maps
Dijkstra cost Quick fact · Graphs
Do the brackets in a line balance? Question · Stacks and queues
Do two sorted prices add up to a target? Question · Two pointers
Does a banner read the same both ways? Question · Two pointers
Does a chain read the same backwards? Question · Linked lists
Does a dependency graph contain a loop? Question · Graphs
Does a root-to-leaf route add up to a target? Question · Trees
Does a tree mirror itself? Question · Trees
Does the chain loop back on itself? Question · Linked lists
Drop the k-th link from the end Question · Linked lists
Dry run Quick fact · Interview craft
Dry run: the first day an account is overdrawn Question · Interview craft
Dynamic programming in four steps Question · Dynamic programming
Each shelf's product of all the other shelves Question · Arrays, strings and hash maps
Evaluate an expression written in postfix order Question · Stacks and queues
Every balanced string of n bracket pairs Question · Backtracking
Every distinct order when songs repeat Question · Backtracking
Every order of a playlist Question · Backtracking
Every selection from a set of toppings Question · Backtracking
Every team of k from n players Question · Backtracking
Fastest delivery time to every depot Question · Graphs
Fewest bookings to cancel so none clash Question · Greedy choices and intervals
Fewest coins to make an amount Question · Dynamic programming
Fewest edits to turn one word into another Question · Dynamic programming
Fewest hops between two stations Question · Graphs
Fewest hops to the last tile Question · Greedy choices and intervals
Fewest one-letter changes between two code words Question · Graphs
Fewest time slots when each job type needs a cooldown Question · Heaps and priority queues
Fill in the water that does not touch the edge Question · Graphs
Find a value in a grid sorted row after row Question · Searching sorted data
Find a value in a rotated sorted list Question · Searching sorted data
Find the balance point of a seesaw Question · Arrays, strings and hash maps
Find the value that fills more than half the list Question · Arrays, strings and hash maps
First and last position of a value in a sorted list Question · Searching sorted data
First order code that appears only once Question · Arrays, strings and hash maps
First place a pattern appears in a text Question · Strings and tries
Fixed-size vs variable-size windows Question · Sliding window
Fold a chain: first, last, second, second-last Question · Linked lists
functools.cache Quick fact · Dynamic programming
Grids are graphs: neighbours, bounds and costs Question · Graphs
Group tile racks that hold the same letters Question · Arrays, strings and hash maps
Half-open intervals Quick fact · Greedy choices and intervals
hash(-1) in CPython Quick fact · Arrays, strings and hash maps
Heap, sort or quickselect? Question · Heaps and priority queues
Heap-style indexes Quick fact · Trees
heapq is a min-heap Quick fact · Graphs
heapq is a min-heap Quick fact · Heaps and priority queues
heapq.heapify Quick fact · Heaps and priority queues
heapq.nlargest and nsmallest Quick fact · Heaps and priority queues
Highest point of a climb-then-descent route Question · Searching sorted data
How a binary heap works Question · Heaps and priority queues
How a hash map keeps lookups fast on average Question · Arrays, strings and hash maps
How big is the search space? Question · Backtracking
How deep is the deepest branch? Question · Trees
How fast can sorting be? Question · Complexity analysis
How linked-list questions give you the chain Question · Linked lists
How many days until a warmer day? Question · Stacks and queues
How many requests arrived in the recent window? Question · Stacks and queues
How many rooms do the bookings need at once? Question · Greedy choices and intervals
How many separate groups does a network have? Question · Graphs
How many words start with a given prefix? Question · Strings and tries
How to tell a problem needs DP Question · Dynamic programming
How trees are written on these pages Question · Trees
In place or a new list: what the interviewer means Question · Two pointers
Input limits hint at cost Quick fact · Interview craft
int() truncates toward zero Quick fact · Stacks and queues
int.bit_count() Quick fact · Bits and maths
int.bit_length() Quick fact · Bits and maths
Is a short route hidden inside a long one? Question · Two pointers
Is every node's left and right height within one? Question · Trees
Is this a valid binary search tree? Question · Trees
itertools.accumulate Quick fact · Sliding window
itertools.combinations Quick fact · Backtracking
itertools.permutations Quick fact · Backtracking
itertools.product Quick fact · Backtracking
Kotlin ArrayDeque Quick fact · Sliding window
Kotlin ArrayDeque Quick fact · Stacks and queues
Kotlin binarySearch Quick fact · Searching sorted data
Kotlin bit operators Quick fact · Bits and maths
Kotlin HashMap vs LinkedHashMap Quick fact · Arrays, strings and hash maps
Kotlin LinkedList Quick fact · Linked lists
Kotlin MutableList swap Quick fact · Two pointers
Kotlin nullable children Quick fact · Trees
Kotlin PriorityQueue Quick fact · Graphs
Kotlin PriorityQueue Quick fact · Heaps and priority queues
Kotlin sortedBy Quick fact · Greedy choices and intervals
Kotlin StringBuilder Quick fact · Strings and tries
Kotlin windowed Quick fact · Sliding window
Largest poster that fits under a skyline Question · Stacks and queues
Largest product of a contiguous run Question · Dynamic programming
Largest total of a contiguous run Question · Greedy choices and intervals
List a tree's values row by row Question · Trees
list.append cost Quick fact · Arrays, strings and hash maps
list.insert(0, x) cost Quick fact · Complexity analysis
list.sort(key=...) Quick fact · Greedy choices and intervals
Longest path between any two nodes Question · Trees
Longest rising sequence of picks from a list Question · Dynamic programming
Longest run of consecutive ticket numbers Question · Arrays, strings and hash maps
Longest shared subsequence of two strings Question · Dynamic programming
Longest single-colour run after repainting k tiles Question · Sliding window
Longest start shared by every word Question · Strings and tries
Longest streak of days within a budget Question · Sliding window
Longest stretch of a log with no letter seen twice Question · Sliding window
Longest stretch that reads the same backwards Question · Strings and tries
Longest stretch with at most two kinds Question · Sliding window
Look up words where '.' stands for any letter Question · Strings and tries
Mark visited when you push or when you pop? Question · Graphs
math.inf for 'impossible' Quick fact · Dynamic programming
math.isqrt Quick fact · Searching sorted data
Median after each new reading Question · Heaps and priority queues
Merge many sorted feeds into one Question · Heaps and priority queues
Merge two sorted shelves into one Question · Two pointers
Minutes until every item on a shelf spoils Question · Graphs
Negative numbers and >> Quick fact · Bits and maths
Number of ways to pay an amount with unlimited coins Question · Dynamic programming
operator.itemgetter Quick fact · Greedy choices and intervals
pow(b, e, m) Quick fact · Complexity analysis
Pre-order, in-order, post-order and level order Question · Trees
Pruning: making exponential searches fast enough Question · Backtracking
Push the empty parking slots to the end Question · Two pointers
Push values into a min-heap by hand Question · Heaps and priority queues
Python list as a stack Quick fact · Stacks and queues
Python list is an array Quick fact · Linked lists
Python recursion limit Quick fact · Trees
Python sort algorithm Quick fact · Two pointers
Python's breakpoint() Quick fact · Interview craft
queue.Queue vs deque Quick fact · Stacks and queues
Raise a number to a huge power, modulo m Question · Complexity analysis
Reading the cost of loops Question · Complexity analysis
Recursion depth and when to walk a tree iteratively Question · Trees
Recursion depth in top-down DP Quick fact · Dynamic programming
Recursion is a stack: converting to an explicit one Question · Stacks and queues
Recursion on long chains Quick fact · Linked lists
Remove repeated readings from a sorted log in place Question · Two pointers
Repaint the connected region of a picture Question · Graphs
Rolling hashes for pattern search Question · Strings and tries
Routes across a grid with blocked cells Question · Dynamic programming
Rubric areas Quick fact · Interview craft
Same-direction vs opposite-end pointers Question · Two pointers
Saving memory with rolling rows Question · Dynamic programming
Seat guests at two tables with no feud at either Question · Graphs
Shift a playlist k places to the right, in place Question · Arrays, strings and hash maps
Shortest run of orders that reaches a goal Question · Sliding window
Slicing copies Quick fact · Two pointers
Slowest reading pace that still finishes on time Question · Searching sorted data
Smallest truck that delivers every parcel in d days Question · Searching sorted data
Smallest value in a rotated sorted list Question · Searching sorted data
Smash the two heaviest rocks until one is left Question · Heaps and priority queues
Sort a tray of three token colours in one pass Question · Two pointers
Sort intervals by start or by end? Question · Greedy choices and intervals
sorted() cost Quick fact · Complexity analysis
sorted() vs list.sort() Quick fact · Two pointers
Sorting tuples Quick fact · Greedy choices and intervals
Space complexity and the call stack Question · Complexity analysis
Split items into two piles of equal weight Question · Dynamic programming
Spot the first repeated badge at the door Question · Arrays, strings and hash maps
Spotting the pattern from the question Question · Interview craft
Squared deviations in sorted order Question · Two pointers
Stack or queue: LIFO and FIFO Question · Stacks and queues
str is immutable Quick fact · Complexity analysis
str.find and in Quick fact · Strings and tries
str.join Quick fact · Strings and tries
str.startswith with a tuple Quick fact · Strings and tries
Strings are immutable Quick fact · Strings and tries
Sum two numbers stored digit by digit Question · Linked lists
Swap every node's left and right children Question · Trees
Swapping in Python Quick fact · Two pointers
Sweep-line thinking Question · Greedy choices and intervals
sys.setrecursionlimit Quick fact · Backtracking
Talking while you code Question · Interview craft
Testing your own code in an interview Question · Interview craft
The backtracking template: choose, explore, undo Question · Backtracking
The cost of building strings Question · Complexity analysis
The cost table for common data structures Question · Complexity analysis
The earliest valid task order Question · Graphs
The first five minutes of a coding interview Question · Interview craft
The k depots nearest the warehouse Question · Heaps and priority queues
The k-th biggest reading Question · Heaps and priority queues
The k-th smallest value in a search tree Question · Trees
The monotonic stack pattern Question · Stacks and queues
The one value without a partner Question · Bits and maths
The placeholder head trick Question · Linked lists
Three-argument pow Quick fact · Bits and maths
Tidy a file path with . and .. parts Question · Stacks and queues
Top three suggestions as you type Question · Strings and tries
Top-down caching or bottom-up tables? Question · Dynamic programming
Trace a word through a letter grid Question · Backtracking
Trie or hash set? Question · Strings and tries
Tuples as heap keys Quick fact · Heaps and priority queues
Turn a chain of links around Question · Linked lists
Two gift prices that hit the budget exactly Question · Arrays, strings and hash maps
Union-find cost Quick fact · Graphs
Union-find: how it works and when to reach for it Question · Graphs
Using bisect and sorted lists in practice Question · Searching sorted data
Ways to cross n stepping stones, one or two at a time Question · Dynamic programming
Ways to read a digit string as letters (1 = A … 26 = Z) Question · Dynamic programming
Weave two sorted chains into one Question · Linked lists
What common Python operations cost Question · Complexity analysis
What makes a good dictionary key Question · Arrays, strings and hash maps
What Python string operations cost Question · Strings and tries
What to do when you are stuck Question · Interview craft
What you see from the right of a tree Question · Trees
When a chain beats a Python list Question · Linked lists
When a sliding window does not work Question · Sliding window
When do two pointers work, and why? Question · Two pointers
When does a greedy choice work? Question · Greedy choices and intervals
Where does a rearranged pattern appear in a text? Question · Sliding window
Where O(log n) comes from Question · Complexity analysis
Where to start a delivery loop so the van never runs dry Question · Greedy choices and intervals
Where would a new price go in a sorted list? Question · Searching sorted data
Which cable closes a loop? Question · Graphs
Which complexity fits which input size Question · Complexity analysis
Which ticket from 0 to n is absent? Question · Bits and maths
Whole-number square root without math.sqrt Question · Searching sorted data
Why a window with a nested loop is still O(n) Question · Sliding window
Why appending to a list is amortized O(1) Question · Arrays, strings and hash maps
Why Dijkstra fails with negative weights Question · Graphs
Why search trees need to stay balanced Question · Trees
Working modulo 10⁹ + 7 Question · Bits and maths
Working out the cost of recursion Question · Complexity analysis
x in list cost Quick fact · Complexity analysis
x in some_list Quick fact · Arrays, strings and hash maps